This invention relates to cold cathode gas laser tubes and more particularly to methods of making high output cold cathode gas laser tubes of reduced size.
Generally, with cold cathode gas laser tubes, typically of the structure including a capillary discharge tube and a hollow cylindrical cold cathode arranged in coaxial partly overlapping relation therewith, the laser light output obtainable increases with the length of the capillary discharge tube. This means that, in order to increase the light output of such laser tubes, the length of the capillary tube used therein should be increased as much as possible. Further, with laser tubes of the type concerned, it is necessary to prevent any discharge concentration on one axial end region of the cylindrical cold cathode which may result in breakage thereof. This requirement may be met, for example, by terminating the capillary tube some distance axially inward from the open end of the cylindrical cold cathode, but this will result in a corresponding decrease in the laser output. On the other hand, in cases where the capillary tube terminates in a position to cause discharge concentration on the cathode end, for example, extending axially beyond the cylindrical cold cathode, use of a tubular capillary-tube overlapping member effective to change the path of discharge extending directly between the adjacent ends of the capillary tube and the cylindrical cold cathode compulsively into one extending between the capillary tube end and an axially inward wall surface of the cold cathode is desirable as it not only is effective to prevent cathode breakage but makes it possible to realize a high output cold cathode gas laser tube with its length fully utilized. Such tubular overlapping member must be supported in the outer envelope of the laser structure in coaxial relation with the capillary tube and the cylindrical cold cathode and necessitates the provision of an appropriate annular supporting flange to serve the purpose. Previously, however, such supporting flange has been formed manually by a so-called "flaring" technique that requires highly skilled labor and much time, causing a substantial rise in cost of fabrication.